Distance Measuring Equipment (DME)

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Components and Characteristics of the Instrument Landing System (ILS)

T-45A UJPT & E2-C2 INav-04

(2) indicates a position approximately 3,500 ft from the landing

threshold and approximately 200 ft AGL above the touch-

down zone

(3) Identification is a coded audio tone (continuous alternating

dots and dashes) and flashing amber cockpit marker light

Inner Marker (IM)

(1) Indicates a point that an aircraft flying a Category II or III

ILS approach is at the designated decision height (DH) on

glidepath between the MM and the landing threshold

(2) Aircraft is approximately 100 ft AGL at IM if on glidepath

and FAC

(3) Identified by a coded audio tone (continuous dots) and a

flashing white cockpit marker beacon light

Back Course (BC)

(1) A BC marker beacon normally indicates an LOC BC final

approach fix (FAF) where the approach glideslope is

intercepted and the descent is commenced

(2) Identified by a coded audio tone (two dots continuously

repeating) and a flashing white cockpit marker light

Marker beacon tones

Fig 3: Marker Beacon

Code/Color

Marker beacons emit specific coded tones, at different pitches,

Identification Table

which the pilot of an ILS/LOC equipped aircraft can monitor

when on the final approach course

In the T-45A, marker beacon tones may be monitored by

placing the "MKR" switch on the communications control panel

to the "ON" position

MKR audio tone volume in the T-45A is preset and cannot be

controlled by the RCVR volume control knob on the

B. Distance Measuring Equipment (DME)

When DME is automatically coupled to the ILS frequency and

specified in the approach procedure, DME may be used:

In lieu of the OM

As a BC final approach fix (FAF)

To establish other fixes on the localizer course

(6-99) Original

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